I played a Burns Artist bass around1961-63 and it and everything else I saw around that time came automatically with flatwound strings. I later changed to a Precision and it also had flatwoulds. I stopped playing for quite a while by which time roundwounds were the norm and my local music shop didn't stock flatwounds. For me roundwounds were virtually unusable on my '63 Precision,I usually play with a pick - when new they could out-twang Duane Eddy. A damper definitly helped and the problems lessened when the strings got older, - I have always maintained the "ashtrays" but am now back on flatwounds and find it less critical whether I use a damper or not. There is no question in my mind that some of the early Jet material used the damper but it may have been removed at times, - indeed for some numbers I install it and for others remove it, - I did the same with the Artist even though I was not aware the Precision had a damper.
An encourageing note is that my local shop now stocks flatwounds and I have managed to persuade a few people to use them !
Des.